1580s, from Greek elephantos, genitive of elephas "elephant" (see elephant) + -iasis "pathological or morbid condition." It refers to two diseases, one characterized by thickening of a body part (E. Arabum), the other, older meaning is "disease characterized by skin resembling an elephant's" (E. Græcorum, also called Egyptian leprosy).

elephantiasis el·e·phan·ti·a·sis (ěl'ə-fən-tī'ə-sĭs)n. Chronic, often extreme enlargement and hardening of cutaneous and subcutaneous tissue, especially of the legs and external genitals, resulting from lymphatic obstruction and usually caused by infestation of the lymph glands and vessels with a filarial worm.